The Drainage Services Department has awarded a $188.8 million contract for adding covers and deodorisation facilities to sedimentation tanks at Stonecutters Island Sewage Treatment Works.

The contract, signed today, is set for completion in late 2012.

Assistant Director of Drainage Services Shiu Wing-yu said the department has in recent years implemented mitigation measures at the plant to reduce odours.

"The addition of covers to the sedimentation tanks will further remove a potential odour source [there] and provide long-term improvement to the air quality of its neighbouring areas," he said.

The contract comprises the supply and installation of 25,000 square metres of fibre reinforced plastic covers to the sedimentation tanks, and two deodorisation plants.

It is the fifth contract awarded under the Harbour Area Treatment Scheme Stage 2A which is a major sewerage infrastructure project. Its commissioning is set for 2014.